Worldwide, most research on alcohol's harms has focused on how heavy drinking harms the drinker himself or herself, since alcohol intake can cause significant acute and chronic harms and premature death. However, recent research has noted that alcohol not only adversely affects the drinker but can also inflict harm on others-family members, friends, acquaintances, and strangers. Only a few types of harms to others (e.g., drink-driving, fetal alcohol effects, intimate partner violence) have been well studied. Thee is a dearth of knowledge about alcohol's broader harms to others (H2O; also known as alcohol's second-hand effects). Initial studies in a few high-income countries (Australia, New Zealand, and the US) show that heavy drinking can hurt families, create financial burdens, reduce quality of life, and engender fears and injuries. These second-hand effects may double the social costs directly incurred by harms to drinkers themselves. Responding to PAR-14- 338 (Secondary Analyses of Existing Alcohol Epidemiology Data R01), the research proposed here will be the first multinational analysis of drinking's harm to others, providing new insight into how differing social and cultural contexts are related to levels, types, and severity of H2O. It will combine surveys from 21 countries of the GENACIS Project (Gender, Alcohol and Culture: An International Study) with surveys from 16 other countries (countries in the WHO-Thai Health collaboration plus separately-funded surveys in additional countries, including the US). The GENACIS surveys provide detailed data on characteristics of drinkers who report causing harms to others, and the WHO-Thai Health and related surveys provide equally detailed data from the victims (both drinkers and nondrinkers) of alcohol-related harms from other heavy drinkers. These surveys were selected to provide a unique asset: data on regional variations in H2O and its correlates within countries. The societies surveyed have a wide range of alcohol policies, drinking cultures, and variation in socioeconomic conditions, including income and gender inequalities. Within a multilevel social ecological framework, we will use these unique data to test hypotheses about (1) individual and contextual factors associated with persons who report having experienced H2O as well as persons who report having caused H2O; (2) regional differences in conditions within countries that may modify individual risks of H2O; and (3) how regional variations in drinking cultures may interact with alcohol policies to prevent or promote harms caused by heavy drinkers. The planned analyses will take advantage of hierarchical linear modeling (including multilevel interaction effects), risk curve analyses and, where appropriate, propensity scoring methods. The proposed analyses will provide the most detailed multinational findings available to date on the individual, social, and cultural influences that ma increase or reduce alcohol's H2O. Using these findings, we aim to identify opportunities for better-focused interventions and policies to reduce alcohol's second-hand effects under a range of environmental conditions, including important new knowledge with direct relevance to the US.